Fizzy icebergs

What's that sound?

Play it to your parents and see if they can guess. Don't let
them see the video!

Have they got it yet?

It's an iceberg.

When icebergs melt they make a fizzing sound. You make your own
fizzing iceberg at home. Here's how you do it:

Put an unopened 1 litre bottle of soda water in the fridge and
leave it overnight.

The next morning, put the bottle in the freezer for around half
an hour until small ice crystals form.

Pour some of the almost frozen soda water in a small paper cup
and put it in the freezer for a few hours. Don't use a china or
plastic cup - it might crack in the freezer.

Once the iceberg is frozen, take it out of the cup.

Put the iceberg in a plastic container or tupperware. Half fill
the container with lukewarm water.

Put the lid on the container.

Can you hear the any sounds?

You should hear fizzing noises, just like in the video. Show
your fizzing iceberg to people and see if they can work out what's
making the noise.

What makes the fizzing noise?

When water freezes into an iceberg, the air bubbles in the water
freeze. As the iceberg melts, the air bubbles pop as they are
released into the water. This makes the fizzing sound.

The carbon dioxide bubbles in your soda water iceberg act like
the air bubbles in a real iceberg. When the soda water freezes,
carbon dioxide bubbles freeze. When the soda water iceberg melts,
the carbon dioxide bubbles pop, in the same way as air bubbles pop
when an iceberg melts. This makes a fizzing noise.